Introduction
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SLVUB16 – February 2017
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Copyright © 2017, Texas Instruments Incorporated
DRV8886AT Evaluation Module User's Guide
A second motor actuation is provided by the
Move # of Steps
and
Reciprocate
commands in which a
programmed number of steps are issued and then the motor is stopped. The acceleration and
deceleration profiles work similarly as before, except when the deceleration starts and when the motor
actually stops are a function of the
Steps to Stop
and deceleration rate parameters.
Figure 7
shows the acceleration profile and the role each parameter plays during speed computation.
Note: Both the WAKE and ENABLE toggle buttons must be green to enable the motor control buttons.
Figure 7. Acceleration Profile
2.6.2
Move Steps
To move the stepper a certain number of steps, use the move steps function to easily perform this action.
Parameters from the other frames are reused and their use is as previously explained. Two new
parameters have been added to properly control the limited number of steps actuation. These parameters
are described as follows:
Number of Steps —
This parameter is the number of steps that the controller will issue.
Steps to Stop —
The controller is continuously monitoring the step being issued and when the current
step is equal to the
Steps to Stop
parameter, a deceleration profile is issued. If the value of the
Steps to Stop
parameter is larger than the number of steps, then the motor stops abruptly and
without undergoing a deceleration profile.
When a deceleration profile is issued, the controller decreases the speed until reaching the value of the
Stopping Speed
parameter. If the
# of Steps
parameter is met before the deceleration profile is complete,
then the motor stops at the current speed. If the stop speed is met before all the number of steps is
issued, then the motor rotates at the stop speed value until all the steps are executed.
Ideally, the system should be tuned to resemble the case in which the controller executes all the
commanded steps at a speed as close as possible to the stop speed. In the event this is not possible
because of the particular parameters that were selected, stopping the motor at a speed very close to the
Stopping Speed
parameter is often good enough to ensure good motion quality and application
performance.
Figure 8
shows the three conditions possible when stopping and the action taken.
